System and method for enhanced physical layer device autonegotiation

ABSTRACT

A system and method for enhanced physical layer device autonegotiation. The autonegotiation process typically identifies the highest common denominator amongst various standardized modes of operation. Enhanced autonegotiation can be used to select a mode of operation that is not the highest common denominator. Enhanced autonegotiation can also identify a non-standardized mode of operation using next page messaging, additional physical signaling, or Layer 2 messaging.

This application is a continuation of non-provisional application Ser.No. 12/569,440, filed Sep. 29, 2009, which claims priority toprovisional application No. 61/223,809, filed Jul. 8, 2009. Each of theabove-identified applications is incorporated by reference herein, inits entirety, for all purposes.

BACKGROUND

1. Field of the Invention

The present invention relates generally to Ethernet systems and, moreparticularly, to a system and method for enhanced physical layer deviceautonegotiation.

2. Introduction

Ethernet devices continue to evolve in capability, including differenttransmission rates (e.g., 10 Mbit/s, 100 Mbit/s, 1 Gbit/s, 10 Gbit/s,etc.), different standards for those transmission rates (e.g.,100BASE-T2, 100BASE-T4, and 100BASE-TX for 100 Mbit/s over copper), anddifferent duplex modes (i.e., half duplex and full duplex) within astandard. Ethernet devices can be designed to function with differentsets of capabilities. Accordingly, a pair of Ethernet devices mustcommunicate with a common set of capabilities to ensureinteroperability.

In one configuration scenario, network administrators can manually setthe speed and duplex mode of each network interface card. While thisprocess can be effective in identifying the particular transmissioncapabilities used by all Ethernet devices in a plant, it is timeconsuming and prone to errors. Efficiency can be gained through the useof an autonegotiation process between a pair of Ethernet devices. Thisautonegotiation process has the potential to remove manual installationerrors. However, autonegotiation is designed to identify a common set oftransmission parameters for a single link, not a common set oftransmission parameters for all Ethernet devices in a plant. Moreover,an autonegotiation process is typically defined only for a particularset of standardized transmission parameters. For example, theautonegotiation process is not designed to allow for negotiation betweennon-standard link rates. What is needed therefore is a mechanism thataddresses the deficiencies of current autonegotiation processes inaccommodating network configuration efforts and ever-evolving Ethernettransmission technologies.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered limiting of its scope, the invention will be describedand explained with additional specificity and detail through the use ofthe accompanying drawings in which:

FIG. 1 illustrates an example of Ethernet physical layer devices (PHYs).

FIG. 2 illustrates an example of retrieving operating mode profileinformation via a network.

FIG. 3 illustrates a flowchart of an autonegotiation process of thepresent invention.

FIG. 4 illustrates an example of an unformatted page used inautonegotiation.

FIG. 5 illustrates a flowchart of an enhanced autonegotiation processusing next page messages.

FIG. 6 illustrates a flowchart of an enhanced autonegotiation processusing additional Layer 2 messages.

DETAILED DESCRIPTION

Various embodiments of the invention are discussed in detail below.While specific implementations are discussed, it should be understoodthat this is done for illustration purposes only. A person skilled inthe relevant art will recognize that other components and configurationsmay be used without parting from the spirit and scope of the invention.

Ethernet has become an increasingly pervasive technology that has beenapplied in various contexts, including twisted pair, backplane, andoptical applications. In general, autonegotiation can be used by a pairof Ethernet devices in identifying which of a plurality of modes ofoperation the pair of Ethernet devices will use. Typically, theautonegotiation process identifies the best possible mode of operation(or highest common denominator) that is shared by the two Ethernetdevices.

The best possible mode of operation is determined from a list of modesof operation that is designed to reflect a variety of priority rules.For example, the list of rank-ordered modes of operation can prefer ahigher speed over a lower speed, and full duplex over half duplex at thesame speed. In general, the list of rank-ordered modes of operation isdesigned to provide the autonegotiation process with a mechanism foridentifying the highest common standardized mode of operation for thatlink.

In the OSI model, autonegotiation resides in the physical layer, whichcan include a PCS (physical coding sublayer), a PMA (physical mediumattachment), and a PMD (physical media dependent). The PCS is generallyresponsible for encoding/decoding to/from code-groups for communicationwith the underlying PMA. In general, the PMA abstracts the PCS from thephysical medium. Accordingly, the PCS can be unaware of the type ofmedium. The primary functions of the PMA include mapping of transmit andreceive code-groups between the PCS and PMA,serialization/de-serialization of code-groups for transmission/receptionon the underlying serial PMD, recovery of clock from the coded data(e.g., 8B/10B, 64B/66B, etc.) supplied by the PMD, and mapping oftransmit and receive bits between the PMA and PMD. The PMD is generallyresponsible for generating electrical or optical signals depending onthe nature of the physical medium connected. PMD signals are sent to themedium dependent interface (MDI), which is the actual medium connected,including connectors, for the various media supported.

In the example of FIG. 1, the autonegotiation is below the PMD. Thisconfiguration is exemplified by an implementation such as 100BASE-TX. Inanother example such as 1000BASE-T, the autonegotiation is included bythe Ethernet device as part of the PCS.

The autonegotiation process has been designed to identify the highestcommon denominator amongst the various standardized modes of operation.These standardized modes of operation represent only a subset of thetotal available modes of operation, which can also include non-standardmodes of operation.

One example of a non-standard mode of operation is a non-standard linkrate. Standard link rates such as 10 Mbit/s, 100 Mbit/s, 1 Gbit/s and 10Gbit/s have been defined. Owing to the order of magnitude increases inthe subsequent generations of link rates, the standard link rates maynot always represent the most practical link rate for a givenapplication.

For example, consider an uncompressed 1080P high-definition videostream, which would require a transmission link rate of approximately 12Gbit/s. One option is to accommodate the 12 Gbit/s video stream in a 10Gbit/s link rate using compression. Another option is to accommodate the12 Gbit/s video stream in a non-standard 12 Gbit/s link rate. One of thebenefits of using a non-standard link rate of 12 Gbit/s would be thereduced power consumption as compared to that required in operating atthe next potential standardized link rate of 40 Gbit/s. As would beappreciated, considerations of power, complexity, and cost have renderednon-standard intermediate link rates such as 2.5 Gbit/s, 5 Gbit/s, etc.as potentially practical solutions for a given application.

Another example of a non-standard mode of operation is a mode ofoperation that accommodates non-standard link distances. TypicalEthernet standards are defined for link distances up to 100 meters for agiven type of cabling. Non-standard modes of operation can also bedefined for short-reach applications (e.g., link distances up to amaximum distance that is less than 100 meters) or broad-reachapplications (e.g., link distances up to a maximum distance that isgreater than 100 meters). Each of these non-standard link distances canbe accommodated using considerations of the constraints of theparticular channel. In one embodiment, reach detection can enhance theautonegotiation process.

A further example of a non-standard mode of operation is asymmetrictransmission. In this non-standard mode of operation, a link can operatein a first standard or non-standard link rate in a first direction andin a second standard or non-standard link rate in a second direction.Consider a scenario of a consumer device designed to handle an inputHDTV stream at a particular port that interfaces with a DVD player. Theinput direction can be designed to operate at a non-standard 12 Gbit/slink rate, while the output direction can be designed to operate at astandard 100 Mbit/s link rate. This scenario illustrates the furtherpossibility of combining different standard and non-standard modes ofoperation onto a particular link.

As would be appreciated, further non-standard modes of operation canalso be defined for a particular Ethernet device. Configuring a givenlink to operate in one of these non-standard modes of operation hastypically required a manual process. It is therefore a feature of thepresent invention that a link can be configured to operate in one of thenon-standard modes of operation using an autonegotiation-based process.

As noted above, a conventional autonegotiation process is used to selectthe highest common denominator from a set of standard modes ofoperation. This conventional autonegotiation process can be deficient inthat the desired mode of operation for a particular link may not equateto the highest common denominator nor one of the standard modes ofoperation.

Consider for example, the case of an autonegotiation process implementedin a plant or installation with a variety of channels. In this context,the desired mode of operation for a particular link would be impacted bythe needs and overall goals of the plant or installation. In otherwords, the desired mode of operation would not be dictated simply by thecapabilities of the Ethernet devices on both ends of the particularlink. For example, the overall goal of the plant or installation mayfocus on power savings, which can dictate that the lowest commondenominator rather than the highest common denominator would be desired.Hence, in one scenario, a 1 Gbit/s link would provide extraneous andunneeded performance when used in a network that is dominated by 100Mbit/s links. This is especially true where the 100 Mbit/s links aremore than sufficient to meet the needs of the various users andapplications within the plant.

In one embodiment of the present invention, the desired range orparticular mode of operation for a link can be specified through amanagement interface. This management interface can be designed tospecify a range or particular mode of operation for various Ethernetdevices in the network. As such, management of the mode of operation ofa network of Ethernet devices can be located in the network (e.g.,distributed).

In one embodiment, a network management protocol such as the SimpleNetwork Management Protocol (SNMP) can be used. Here, the managementfunction within a network management station can be enabled using a userinterface, which can control the network management application. Thenetwork management application, in turn, can communicate with softwareagents in various systems over the network.

Regardless of the particular layer at which the management control iseffected, a register, programmable read only memory (PROM), etc. that isaccessible by the Ethernet device can be programmed with a range orparticular mode of operation. This programmed range or particular modeof operation can be used alone or in combination with theautonegotiation process to determine the mode of operation of theEthernet device.

In one embodiment, the desired mode of operation for a particularEthernet device is stored as part of a network profile for that Ethernetdevice. FIG. 2 illustrates an example of such a configuration where modeof operation profile information can be retrieved from a networkdatabase. As illustrated, local link partner 220 is in communicationwith remote link partner 210 over a link. In one example, local linkpartner 220 can represent a switch, which supports a plurality of linkpartners. As would be appreciated, the link can be part of a LAN, MAN,WAN, wholly managed private network (e.g., VPN), etc.

In the autonegotiation process, local link partner 220 can accessprofile database 250 via server 240, which is linked to local linkpartner 220 via intranet 230. As would be appreciated, the contents ofprofile database 250 need not be centralized, but can be cached orotherwise distributed across different parts of the network.

The access of profile database 250 by local link partner 220 during theautonegotiation process can be based on identifying information (e.g.,user, device, etc.) that is associated with itself or remote linkpartner 210. For example, the access of profile database 250 can bebased on a user identifier, MAC address, or any other identifyinginformation. Through the access of profile database 250, theautonegotiation process associated with local link partner 220 canretrieve autonegotiation management information that can be used todetermine the common mode of operation between local link partner 220and remote link partner 210. In various embodiments, access to profiledatabase 250 is facilitated by a Layer 2 or Layer 3 mechanism.

To illustrate the usage of management information in the autonegotiationprocess, reference is now made to the flowchart of FIG. 3. Asillustrated, the process of FIG. 3 begins at step 302 where an Ethernetdevice retrieves management information that specifies a range orparticular mode of operation. As noted above, the management informationcan be retrieved from a register, PROM, network database, or the like.

At step 304, the local link partner then modifies the autonegotiationinformation with the retrieved management information. In one example,the autonegotiation information can represent the base link code wordthat specifies the actual capabilities of the Ethernet device. Thisautonegotiation information can be modified using the managementinformation. For example, the management information can specify aparticular mode of operation that represents one of the modes ofoperation indicated by the original base link code word. The resultingmodified autonegotiation information can therefore reflect a modifiedbase link code word that indicates only a single supported mode ofoperation. In effect, the modified base link code word can advertise asubset of the actual capabilities of the Ethernet device.

At step 306, the modified autonegotiation information is then advertisedto the partner Ethernet device. Through this exchange of autonegotiationinformation, a common mode of operation can then be identified at step308. It is a feature of the present invention that the managementinformation can be used to direct the autonegotiation process to aresult that is not necessarily the highest common denominator.

Where a preferred operating mode is specified, the specifiedconfiguration can be used by the autonegotiation process as a ceilingfor the mode of operation. The modes of operation that have a link rategreater than the specified maximum link rate would be excluded from theadvertised supported modes of operation even though the Ethernet devicecan support it. This would dictate that a lower-priority configurationwould be agreed upon even though other higher-priority configurationswould be in common between the Ethernet devices in the link. In anotherexample, a specified range of modes of operation can be used by theautonegotiation process in restricting the available choices of theautonegotiation process to the specified range of modes of operation. Ingeneral, the programmed range or particular mode of operation can beused to eliminate choices that would otherwise be available to theautonegotiation process.

As has been described, a specified range or particular mode of operationcan be used to limit the autonegotiation process from automaticallyselecting the highest common denominator. As will be described below,supplemental communication can also be used as part of theautonegotiation process to select a non-standard mode of operation foruse between a linked pair of Ethernet devices.

Conventionally, the autonegotiation process is used to select from a setof known, standardized modes of operation. An Ethernet device'scapability of supporting these known, standardized modes of operationcan be advertised using selected bits in one or more pre-definedautonegotiation message formats. As noted, non-standardized modes ofoperation are typically selected manually, as those non-standardizedmodes of operation are not included in the pre-defined autonegotiationmessage formats.

It is a feature of the present invention that a non-standardized mode ofoperation can be selected using one or more unformatted next pagemessages as part of the autonegotiation process. Automated as comparedto manual selection of a non-standardized mode of operation between apair of Ethernet devices is thereby enabled.

FIG. 4 illustrates a format of an unformatted next page message. In theautonegotiation process, one or more of these unformatted next pagemessages would be sent in addition to the predefined messages (e.g.,base link code word) that are used in the identification of the standard10/100/1000 modes of operation. By this process, an augmentedautonegotiation process would result, wherein the search for a commonmode of operation would include the standard modes of operation as wellas the additional non-standard modes of operation that are identifiedusing the data in the unformatted next page messages.

To further illustrate this feature of the present invention, referenceis now made to the flowchart of FIG. 5. As illustrated, the processbegins at step 502 where an Ethernet device transmits one or moreautonegotiation messages that indicates a capability of the Ethernetdevice to support standardized modes of operation. Standardized modes ofoperation can include 1000BASE-T full duplex, 1000BASE-T half duplex,100BASE-T2 full duplex, 100BASE-TX full duplex, 100BASE-T2 half duplex,100BASE-T4, 100BASE-TX half duplex, 10BASE-T full duplex, 10BASE-T halfduplex, etc. For example, 10BASE-T half duplex and 10BASE-T full duplexmodes of operation can be indicated by bits 0 and 1, respectively, inthe base link code word.

In addition to the transmission of one or more autonegotiation messagesthat indicates a capability of the Ethernet device to supportstandardized modes of operation, the Ethernet device also transmits oneor more autonegotiation messages that indicates a capability of theEthernet device to support non-standardized modes of operation. Asnoted, non-standardized modes of operation can include non-standard linktransmission rates (e.g., 12 Gbit/s), short-reach mode of operation,long-reach mode of operation, asymmetric operation, etc. In one example,the indications of the capability to support the non-standardized modesof operation can be provided in bits 0-10 of the next page message ofFIG. 4. As would be appreciated, the specific mechanism by which bits0-10 would be used to indicate support for such non-standardized modesof operation would be implementation dependent. Further, the number ofnon-standardized modes of operation being advertised can dictate theparticular number of next page messages that are needed to advertisesuch capabilities. In general, the specific number of unformatted nextpage message used can depend on the type of information that istransmitted.

The transmission of autonegotiation messages that advertise capabilitiesto support both standardized and non-standardized modes of operationenables a pair of Ethernet devices to automatically identify a commonmode of operation from the non-standardized modes of operation inaddition to the standardized modes of operation. Upon the exchange ofadvertised capabilities, the Ethernet device can then select anon-standardized mode of operation for use at step 506.

In another embodiment, a non-standardized mode of operation can beselected using physical signaling in addition to the conventionalautonegotiation signaling (e.g., link pulses). While the specific formof physical signaling would be implementation dependent, the physicalsignaling can be designed to supplement or even replace the conventionalautonegotiation signaling by providing information regarding additionalnon-standardized modes of operation that may be in common between thetwo Ethernet devices.

In one scenario, a set of physical signals different from theconventional autonegotiation signals is used. For example, theconventional autonegotiation signaling may not go as far as needed(e.g., broad reach applications) or may not be used over older cabling.In accordance with the present invention, the physical signaling can beused alone or in conjunction with existing autonegotiation signals tofacilitate selection of an operating mode from a mix of variousoperating modes.

In yet another embodiment, a non-standard mode of operation can beselected using Layer 2 messaging. Here, the autonegotiation process canbe used to identify an initial mode of operation. This initial mode ofoperation can represent a minimum or base-level of commonality betweenthe two Ethernet devices. After the initial mode of operation isestablished, the Layer 2 messaging can be used to identify a commonstandardized or non-standardized mode of operation that can be used onthe link.

FIG. 6 illustrates further illustrates such a process. As illustrated,the process begins at step 602 where autonegotiation is used to select abase mode of operation. In one example, this base mode of operation canrepresent a minimum set of functionality for the Ethernet devices. Thisminimum set of functionality can be identified using a baseautonegotiation message alone or in combination with additionalautonegotiation messages. The particular base mode of operation would beimplementation dependent, and is needed to establish a framework forfurther communication between the Ethernet devices.

Once the base mode of operation is established between the Ethernetdevices, Layer 2 messaging can be exchanged at step 604. This Layer 2messaging can be used to identify available non-standardized modes ofoperation that are supported by both Ethernet devices. As would beappreciated, Layer 2 messaging would not require standardized messagingformats such as those in the conventional autonegotiation process. Basedon the messaging exchange, a common non-standardized mode of operationcan then be selected at step 606 for use between the two Ethernetdevices.

In general, the autonegotiation process can be implemented as atwo-stage negotiation. The first stage of negotiation can be used toidentify a base mode of operation. Establishment of this base mode ofoperation would facilitate the implementation of other enhancements aspart of the second stage of negotiation. As would be appreciated, theparticular types of enhancements would be implementation dependent andcan relate to any characteristic of the mode of operation between thedevices.

As has been described, the enhanced autonegotiation process of thepresent invention can be used to select from a mix of standardized andnon-standardized modes of operation. In general, the principles of thepresent invention can also be used to autonegotiate to a variable rate.For example, each PHY can test the channel and exchange informationregarding the channel (e.g., type of cable, length of cable, etc.) thatcan be used to select a variable rate (e.g., more than 1 G but less than10 G depending on the type and length of cable).

It should be noted that the principles of the present invention can beapplied to various PHY applications including twisted pair, backplane,optical, point-to-multipoint, etc. The principles of the presentinvention can also be applied to passive optical networks (PONs).Moreover, the principles of the present invention can be applied tovarious standard link rates (e.g., 10 Mbit/s, 100 Mbit/s, 1 Gbit/s, 10Gbit/s, 40 Gbit/s), non-standard link rates (e.g., 2.5 Gbit/s, 5 Gbit/s,20-30 Gbit/s, etc.), and future link rates (e.g., 100 Gbit/s and greaterthan 100 Gbit/s).

These and other aspects of the present invention will become apparent tothose skilled in the art by a review of the preceding detaileddescription. Although a number of salient features of the presentinvention have been described above, the invention is capable of otherembodiments and of being practiced and carried out in various ways thatwould be apparent to one of ordinary skill in the art after reading thedisclosed invention, therefore the above description should not beconsidered to be exclusive of these other embodiments. Also, it is to beunderstood that the phraseology and terminology employed herein are forthe purposes of description and should not be regarded as limiting.

What is claimed is:
 1. A method, comprising: transmitting, from a firstEthernet device to a second Ethernet device, first signals that indicatea capability of said first Ethernet device to support a short reach modeof operation that is configured for link distances up to a maximum linkdistance that is less than 100 meters or a long reach mode of operationthat is configured for link distances up to a maximum link distance thatis greater than 100 meters; receiving, from said second Ethernet device,second signals that indicate a capability of said second Ethernet deviceto support said short reach mode of operation or said long reach mode ofoperation; and selecting, by said first Ethernet device based on saidreceived second signals, one of said short reach mode of operation orsaid long reach mode of operation for use by said first Ethernet device.2. The method of claim 1, wherein said transmitting comprisestransmitting after transmitting messages that indicate 10/100/1000capabilities of said first Ethernet device.
 3. The method of claim 1,wherein said selecting comprises selecting a mode of operation having alink transmission rate that is greater than 10 Mbit/s and less than 100Mbit/s, greater than 100 Mbit/s and less than 1 Gbit/s, or greater thanthan 1 Gbit/s and less than 10 Gbit/s.
 4. The method of claim 1, whereinsaid selecting comprises selecting a symmetric mode of operation.
 5. Themethod of claim 1, wherein said selecting comprises selecting anasymmetric mode of operation.
 6. The method of claim 1, wherein saidtransmitting comprises transmitting an autonegotiation next pagemessage.
 7. A method, comprising: transitioning, based on a successfulcompletion of a negotiation process between a first Ethernet device anda second Ethernet device, said first Ethernet device to a base mode ofoperation to facilitate communication between said first Ethernet deviceand said second Ethernet device; transmitting, by said first Ethernetdevice to said second Ethernet device, additional signals that includeinformation that identifies support by said first Ethernet device of asecond mode of operation different from said base mode of operation; andupon a determination that said second Ethernet device also supports saidsecond mode of operation, transitioning said first Ethernet device fromsaid base mode of operation to said second mode of operation.
 8. Themethod of claim 7, further comprising identifying said base mode ofoperation using one or more autonegotiation messages.
 9. The method ofclaim 7, wherein said transmitting comprises transmitting Layer 2messages.
 10. The method of claim 7, wherein said second mode ofoperation has a link transmission rate that is greater than 10 Mbit/sand less than 100 Mbit/s, greater than 100 Mbit/s and less than 1Gbit/s, or greater than 1 Gbit/s and less than 10 Gbit/s.
 11. The methodof claim 7, wherein said second mode of operation is a short-reach modeof operation designed for link distances up to a maximum link distancethat is less than 100 meters.
 12. The method of claim 7, wherein saidsecond mode of operation is a long-reach mode of operation designed forlink distances up to a maximum link distance that is greater than 100meters.
 13. The method of claim 7, wherein said second mode of operationis an asymmetric mode of operation.